Ok, I allways have noticed that my car does not have the punch it should at lower rpms(2000-2500). But lately the car bucks at full throttle in 4 gear at higher rpm and the other night it felt like the car hit the limiter at around 5200rpm, it very slowly pulled to redline. The thing is it is fine at high rpm in 1st, 2nd and 3rd. The car also idles perfectly at 800rpm. The car doesn't backfire, just some popping but thats just when cruising. The car is hard to turn over when its warm, but not when its cold. What do you guys think? FYI its a 93 z28 with 6 spd and 3.23 gears I changed the fuel filter a couple of months ago.

 

Hesitation, stumbling--- I don't know if this will help... Mine was stumbling and it sounded like I had a valve tap. It shook when I gave it gas on the highway and it was running very badly at low rpms after it warmed up. I went nuts trying to find the problem. I had a similar problem with my Plymouth Voyager for a long time.... Yup, I use the same gas station for both cars... I put in Sunoco 94 and a bottle of STP fuel injection cleaner. My LT1 is running like a dream. No tapping at all, no hesitation, ready for race day...And my voyager... I still give it the cheap gas, who cares right? Remember, in the winter time a lot of areas switch to oxygenated gas mixture.

 

same symptoms...everyone said it was my opti screwing up. Tried plugs and wires....but that didn't work.